Issue #1404 Random crash with Shaper. REDISPLAY is not flushed in deleteFeature. It improves the application performance. Problem case is "Delete" in Sketch: create a rectangle, a lenght, select a line, after a lenght(or with rectangle so, that the line is the first), call Delete action. Result: warning message(in Debug mode) about empty AIS(it's caused a crash).
Additionaly performance of fillet, mirror, rotation are improved by this modification.
